The present invention relates generally to integrated semiconductor circuits and more specifically to a device for the configuration of options in an integrated circuit and to an associated method of implementation.
For reasons of manufacturing cost, it would be desirable to increase the number of options available in one integrated circuit. In a given range of products, a single circuit with several options would enable the replacement of several different integrated circuits. Thereby, the cost of design and manufacture would be reduced. It is thus desirable to provide users of circuits with wider possibilities of configuration and hence of use, to reduce the demand for customized circuits which are costly to make.
One solution to this need is to provide an option configuration device in an integrated circuit. This device is electrically programmable to enable the user to configure his circuit himself.
Usually, the configuration device comprises electrically programmable non-volatile memory elements associated with latch elements. In general, for each option bit, the corresponding configuration circuit comprises two non-volatile memory cells, one at each input of the latch. In the initial state, when each integrated circuit comes off the production line, the two memory cells are blank. The configuration consists in programming one of the cells. Depending on the cell that is programmed, an option configuration bit is obtained at output of the latch equal to 0 or to 1. This bit is applied to the management circuitry of the corresponding option.
One drawback of these option configuration devices with non-volatile memory cells and latches is that it is possible that a cell that has been programmed changes its state, following leakages of current or a parasitic phenomenon of programming or erasure known as "soft programming" or "soft erasing" which may occur when the cell is biased in the read mode. The option bit then assumes a false value. The result is a problem of reliability of the integrated circuits with option configuration.